Implantable medical devices (IMDs) are commonly used to provide treatment to patients. Implantable medical devices can include cardiac rhythm management devices and neurological stimulation devices, amongst others. Some types of implantable medical devices deliver electrical stimuli to a target tissue via a lead wire (“stimulation lead”) or catheter having one or more electrodes disposed in or about the target tissue. The stimulation lead is frequently connected to a pulse generator housing via a structure commonly referred to as a header assembly. The header assembly serves to provide fixation of the proximal end of the stimulation lead and electrically couples the stimulation lead with the pulse generator.
During the procedure of implanting the implantable medical system, the stimulation leads are generally introduced through a major vein (typically the subclavian vein) in the upper chest and into the heart with the help of imaging devices. The distal ends of the stimulation leads include electrodes and transvenously pass to the heart. Once the stimulation leads are in the proper position, they are coupled to the pulse generator via the header assembly. Specifically, the proximal ends of the stimulation leads are inserted into ports in the header assembly and then secured in place, typically with a set screw.
A specially adapted torque wrench is used by the surgeon to screw each set screw into position. For leads with two electrodes, one set screw presses a tip electrode into its contact within the header assembly while another set screw presses a ring electrode into its contact within the header assembly. The torque wrench is designed to ensure that the proper amount of force is applied to the set screw. If a larger than necessary force is applied, the outer housing of the torque wrench rotates and ratchets against an inner component. The ratcheting action provides tactile and audible feedback to the surgeon that the set screw has been sufficiently tightened.